Camera shake correction apparatuses provided in conventional digital cameras calculate a camera shake amount by integrating acceleration detected by a gyro sensor and displaces a lens, an apex-angle prism, an image device, or the like, so as to compensate this camera shake amount.
The invention disclosed in Japanese Patent No. 3143527, as one example of such camera shake correction apparatuses, comprises apex-angle sensors (43, 44 (gyro sensor, or the like)) that detect camera shakes, a variable apex-angle prism (41) that is deformable to change a light axis, actuators (48, 49) that deform the variable apex-angle prism (41), a control circuit that applies driving voltage to the actuator, and the like.
The invention deforms the variable apex-angle prism (41) to change the light axis via the actuators (48, 49) according to the signals detected by the apex-angle sensors (43, 44).
Furthermore, Japanese Patent No. 3143527 comprises a light receiving means (8 (two-dimensional position sensor)) for detecting a light axis variation angle, a circuit that detects the output signals of the apex-angle sensors (43, 44), and the like, and discloses the invention for evaluating the performance of a camera shake correction apparatus from the relationship between the driving voltage and the light axis variation angle, the relationship between apex-angle detection sensor output and the light axis variation angle, and the like.
So it can be considered that the camera shake of a commercially-available digital camera is evaluated using this invention. In this case, however, it is necessary to add a means for detecting the above light axis variation angle to the digital camera itself or connect the former to the digital camera. So the evaluation is distant because it is difficult to apply the invention to camera shake measurement of an optional digital camera.
Moreover, in the above case, detectable camera shake directions are limited depending on the direction in which a gyro sensor is installed, and it is further difficult to observe time-series changes of a camera shake direction and a camera shake amount.
By the way, in general, camera shakes that occur when a subject is photographed with a still camera are classified into three types: a camera shake that serves as rotational movement around a pan axis (vertical axis), a camera shake that serves as rotational movement around a pitch axis (horizontal axis), and a camera shake that serves as rotational movement around a roll axis (axis perpendicular to both the pan axis and the pitch axis). The pitch axis may also be referred to as a tilt axis.
These three types of camera shakes are considered to differ, depending on various conditions such as a shutter button location, a camera shape, whether a user is male or female, and whether the user is professional or amateur.
The camera shake correction functions of typical commercially-available digital cameras detected and corrected only the camera shake amounts around the pitch axis and pan axis but did not detect and correct camera shakes around the roll axis (light axis) (for example, see FIG. 9 in Japanese Patent No. 3143527).
This is because detection of camera shakes around the roll axis requires that a gyro sensor be installed in the digital camera thickness direction and this installation contributes to the hindering of smaller digital cameras and lower cost.
Therefore, only light axis variation angles around the pitch axis and pan axis are obtained even if a means for detecting a light axis variation angle in Japanese Patent No. 3143527 is connected to a conventional digital camera. It is difficult to detect triaxial rotational movement that is an actual camera shake phenomenon.
Also, the camera shake correction measurement apparatus described in Japanese Patent Application KOKAI Publication No. 2002-195815 is available, for example, as other pertinent art. This conventional art is configured to pass the laser beam (L) projected from a light source (101) through an optical system (103) having a camera shake correction function, projecting the laser beam to a scale (106), and measuring the moving amount of an image on the projected scale, thereby evaluating the performance of said camera shake correction function.
Even this conventional art can obtain only a single point to be projected to the scale (106) or a rectilinear-trajectory on a two-dimensional surface. It could not detect triaxial rotational movement corresponding to the actual camera shake phenomenon and time-series changes of a camera shake direction and a camera shake amount.
In addition, the camera shake correction method and image monitoring system described in Japanese Patent Application KOKAI Publication No. 10-23322, for example, as other pertinent art, define one of the two frames in images photographed by a surveillance camera as a reference image and the other as a processed image and correct image shifts by performing pattern matching for the processed image using a template pattern created from the reference image, selecting a specific matching region using the regularity of image shifts resulting from camera shake, and calculating a camera shake amount from the moving vector thereof.
However, this conventional art uses any single image photographed by the surveillance camera as the reference image, and performs pattern matching for the processed image using the template pattern created from the reference image. In such a configuration, only rectilinear-trajectory on a two-dimensional surface is obtained as the camera shake amount, so this conventional art could not detect triaxial rotational movement corresponding to the camera shake phenomenon of the still camera and time-series changes of a camera shake direction and a camera shake amount, like the inventions described in other patent literatures.